Ultrasound-guided ablation catheter and methods of use

ABSTRACT

The present invention provides ultrasound-guided ablation catheters and methods for their use. In one embodiment, a tissue ablation apparatus ( 2 ) includes a flexible elongate body ( 12 ) having proximal ( 14 ) and distal ( 12 ) ends. A plurality of spaced-apart electrodes ( 24 ) are operably attached to the flexible body near the distal end. A plurality of transducer elements ( 28 ) are disposed between at least some of the electrodes. Transducers assist the physician in determining whether or not the ablation elements are in contact with the tissue to be ablated.

This application is a continuation of application Ser. No. 09/227,281,filed Jan. 6, 1999 now U.S. Pat. No. 6,206,831.

BACKGROUND OF THE INVENTION

The invention relates generally to the field of ablation catheters, andin particular, to ultrasound-guided ablation catheters.

Physicians make use of catheters today in medical procedures that arebest performed by gaining access into interior regions of the body. Forexample, in electrophysiological therapy, ablation is used to treatcardiac rhythm disturbances. Such a therapy may be used, for instance,to treat atrial fibrillation by forming long, thin lesions of differentcurvilinear shapes in heart tissue.

During these procedures, a physician steers a catheter through a mainvein or artery into the interior region of the heart that is to betreated. An ablation element carried on the distal end of the catheteris positioned near the tissue that is to be ablated. For suchtreatments, the delivery of ablating energy must be closely governed toavoid incidence of tissue damage and coagulum formation. Further, theablation catheters must be precisely positioned adjacent to andpreferably in contact with the tissue to be treated, to insure thelesions are properly located.

Physicians and staff performing diagnostic and therapeutic procedures,such as electrophysiological therapy, typically require an imagingsystem to assist them in positioning the ablation catheter.Mini-transesophageal echocardiography (mini-TEE) probes are available,however, these probes must be swallowed or inserted down the patient'sthroat. Such probes are poorly tolerated by patients unless they arefully anesthetized. Further, these probes can be rather large (i.e., 20French in diameter), use complex transducer configurations and may havedifficulty in detecting tissue contact by the ablation elements.

Hence, it is desirable to provide an effective apparatus which assiststhe physician in determining whether the ablation elements are incontact with the tissue to be ablated. It is further desirable to havesuch imaging systems small enough to enter narrow and tortuous regionsof the patient's vasculature. It is further desirable to have suchimaging systems be located coincidental with the ablation elements toensure tissue contact prior to ablation.

SUMMARY OF THE INVENTION

The present invention provides ultrasound-guided ablation catheters andmethods for their use. Catheters and systems of the present inventionwill be particularly useful for precise positioning of ablationcatheters prior to ablation of cardiac tissue, such as that required forthe treatment of atrial fibrillation. Systems of the present inventionuse ultrasound transducers in the distal end of an ablation catheter toassist the operator in determining whether or not the ablation elementsare in contact with the tissue to be ablated.

In one embodiment, the present invention provides a tissue ablationapparatus comprising a flexible elongate body having a proximal end anda distal end. A plurality of spaced-apart electrodes are operablyattached to the flexible body near the distal end. A plurality oftransducer elements are disposed between at least some of theelectrodes. In this manner, transducer elements are positioned to assistthe physician in detecting whether or not tissue contact is made by theproximate electrodes.

In one aspect, each electrode has at least one transducer elementadjacent thereto. Preferably, the electrodes and transducer elements areoperably attached to the flexible body in an alternating fashion. Stillmore preferably, the number of transducer elements exceeds the number ofelectrodes by at least one. In this manner, each electrode would have atransducer element distal thereof and another transducer elementproximal thereof. By determining that the transducer elements are incontact with the tissue, the physician can presume that the interveningelectrode is similarly in contact with the tissue.

In one aspect, the ablation apparatus further includes a plurality ofinsulators operably attached to the flexible body. The insulatorsoperate to insulate the transducer elements from the electrodes. In oneparticular aspect, the flexible body has an outer diameter that is lessthan about eight (8) French. Ablation apparatus having such a size aresufficiently small enough to pass through the tortuous regions of apatient's vascular system.

In one aspect of the present invention, the electrodes are spaced apartfrom adjacent electrodes by a gap, preferably, a gap that is betweenabout 1.5 mm and about 3.0 mm. Preferably, at least one of thetransducer elements is operably attached to the flexible body in eachgap. In this manner, transducer elements and electrodes are operablyattached to the body in an alternating fashion.

In one particular aspect, the transducer elements comprise cylindricaltransducer elements. The cylindrical elements each have a throughhole,and the elements are positioned so that a longitudinal axis of theflexible body passes through the throughholes. In this manner, thetransducer elements present a 360 degree outer surface to thesurrounding tissue. Therefore, the transducer elements need not berotated to produce an image within a 360° image plane. In anotheraspect, the electrodes comprise generally cylindrical electrodes havingan inner surface and an outer surface. The electrodes are positioned sothat the inner surfaces face the longitudinal axis of the flexible body.

In one particular aspect, the apparatus includes between about two andabout fourteen electrodes, and between about three and about fifteentransducer elements. Preferably, the electrodes and transducer elementsare adapted to be connected to a controller. An ablation apparatusfurther preferably comprises a temperature sensing element operablyattached to the flexible body. Such temperature sensing elements may beused, for example, to help monitor tissue temperatures near the ablationelements.

The invention further provides an exemplary system for ablating tissue.The system comprises an ablation apparatus ostensibly as previouslydescribed. The system includes a controller in electrical communicationwith the ablation elements and the transducer elements. In one aspect,the ablation elements comprise a plurality of electrodes. Alternatively,the ablation elements comprise a plurality of ablation transducerelements. In this manner, ablation may occur through the use of RFablation or through ultrasound ablation. An exemplary description ofacoustic ablation using transducer elements is described in U.S. Pat.No. 5,630,837, the complete disclosure of which is hereby incorporatedby reference. It will be appreciated by those skilled in the art thatother ablation elements may be used within the scope of the presentinvention.

Preferably, the controller comprises an ultrasound imaging and ablationcontroller. In this manner, ultrasound imaging is used to detect tissuecontact by the ablation apparatus. The ablation of desired tissue thencan occur.

In one aspect, the system further includes a plurality of leads with atleast one lead operably attached to each of the ablation elements andeach of the transducer elements. The plurality of leads preferably arein electrical communication with the controller to permit electricalsignals to be transmitted from the controller to the ablation andtransducer elements. The leads also permit signals to be sent from thetransducer elements to the controller.

In a particular aspect, the system further includes a multiplexeroperably attached to the flexible body, preferably near the distal end,and in electrical communication with the controller. At least some ofthe leads are operably attached to the multiplexer. The multiplexeroperates to determine which transducer element receives electricalsignals from the controller. By using a multiplexer at the distal end,the number of wires connecting the controller to the distal end may bereduced. By reducing the number of wires passing through an interiorlumen of the flexible body, the outer diameter of the flexible bodylikewise can be reduced. Such a multiplexer will be particularlybeneficial for apparatus having a relatively large number of transducerelements which together would use more wires than the multiplexer.

In one particular aspect, the transducer elements comprise cylindricaltransducer elements. In this manner, the transducer elements need not berotated to produce images within an image plane.

The invention further provides a method of ablating tissue. The methodincludes providing a tissue ablation apparatus as previously describedwith the electrodes and transducer elements being in electricalcommunication with a controller. The ablation apparatus is inserted intoa patient and positioned proximate a tissue to be ablated. Thetransducer elements are energized and a plurality of reflected signalsare received from the transducer elements. The method includesprocessing the reflected signals with the controller to determine if thetransducer elements are in contact with the tissue to be ablated. If thecontroller determines that at least one of the transducer elements is incontact with the tissue, at least one of the electrodes is activated toablate the tissue.

In one aspect, an ablation apparatus is provided having transducerelements and electrodes operably attached to the body in an alternatingfashion. In another aspect, the reflected signals are processed todetermine if one of the transducer elements is in contact with thetissue. If one of the transducer elements is in contact with the tissue,an adjacent electrode is activated to ablate the tissue.

In one aspect of the method, the reflected signals are processed todetermine if all of the transducer elements are in contact with thetissue. In still another aspect, the method further includesrepositioning the ablation apparatus if the controller determines thatat least one of the transducer elements is not in contact with thetissue. In still another aspect, the ablation apparatus further includesa multiplexer operably attached to the body and in electricalcommunication with the transducer elements. The multiplexer operates tocoordinate the order in which the transducers are energized.

The invention further provides a method of ablating tissue including thestep of providing a tissue ablation apparatus having an elongate body, aplurality of ablation elements and a plurality of transducer elements.The ablation and transducer elements are operably attached to the bodyin an alternating fashion. The method includes inserting the ablationapparatus into a patient and positioning the ablation apparatus withinthe patient so that the ablation apparatus is proximate a tissue to beablated. The transducer elements are energized and a plurality ofreflected signals are received from the transducer elements. The methodincludes processing the reflected signals to determine if the transducerelements are in contact with the tissue to be ablated and activating atleast one of the ablation elements to ablate the tissue if thecontroller determines that at least one of the transducer elements is incontact with the tissue.

In one aspect, the transducer elements are activated to ablate tissueusing ultrasound energy. In another aspect of the method, the ablationelements include a plurality of electrodes for supplying current to thetissue. Alternatively, the ablation elements comprise a plurality ofablation transducers that operate to ablate the tissue using ultrasoundenergy.

Other features and advantages of the invention will appear from thefollowing description in which the preferred embodiment has been setforth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an overall view of a system for ablating tissue accordingto the present invention;

FIG. 2 depicts the distal end of a flexible elongate body as part of atissue ablation system of the present invention;

FIG. 3 depicts a cross-sectional side view of the flexible elongate bodyshown in FIG. 2;

FIG. 4A depicts a cross-sectional end view of the flexible body shown inFIG. 3, taken along line 4A—4A;

FIG. 4B depicts an overall view of a cylindrical transducer element aspart of a tissue ablation apparatus according to the present invention;

FIGS. 5A and 5B depict alternative embodiments of the tissue ablationapparatus according to the present invention;

FIG. 6 depicts a schematic of a multiplexer as part of a tissue ablationapparatus;

FIGS. 7A-7B depict energizing and reflected signals sent to and receivedby a transducer element of the present invention; and

FIG. 8 depicts the tissue ablation apparatus of the present invention incontact with tissue.

A DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 depicts an exemplary tissue ablation apparatus 2 as part of atissue ablation system 4 according to the present invention. Ablationapparatus 2 comprises a flexible elongate body 12 having a distal end 10and a proximal end 14. Proximal end 14 includes a handle 16 containing asteering mechanism 18. Steering mechanism 18 includes a steering lever22 which operates a cam wheel (not shown) to maneuver flexible distalend 10 as shown by the arrows in FIG. 1. System 4 includes a connector20 which connects with a controller 23 for operation of ablationapparatus 2 as further described below. Controller 23 is capable ofproviding electrical input to ablation apparatus 2 as needed to imageand ablate within a patient's body. It will be appreciated by thoseskilled in the art that steering mechanism 18 can vary from that shownin FIG. 1 within the scope of the present invention. Exemplary steeringmechanisms are described in International Application No.PCT/US94/11748, the complete disclosure of which is hereby incorporatedby reference for all purposes.

Tissue ablation apparatus 2 depicted in FIG. 1 will be particularlyuseful in the treatment of atrial fibrillation by positioning distal end10 within a desired region of the heart. To enter the right atrium, thephysician can direct elongate body 12 through a conventional vascularintroducer through the femoral vein. For entry into the left atrium, thephysician can direct elongate body 12 through a conventional vascularintroducer retrograde through the aortic and mitral valves. For thetreatment of atrial fibrillation, it is believed that formation of longthin legions of different curvilinear shapes is required. Catheters andablation apparatus 2 of the present invention may be used to ablateheart tissue containing abnormal electrical pathways, such asarrhythmogenic foci. Further details of tissue ablation apparatus 2 areshown in FIGS. 2 and 3.

FIGS. 2 and 3 depict elongate body 12 having a plurality of spaced-apartablation elements 24, each separated by a gap 26 from adjacent ablationelements 24. Interspaced amongst ablation elements 24 are a plurality oftransducer elements 28. Preferably, ablation elements 24 and transducerelements 28 are operably attached to body 12 in an alternating fashion.Ablation apparatus 2 preferably includes between about two and aboutfourteen ablation elements, and between about three and about fifteentransducer elements. More preferably, apparatus 2 has at least one moretransducer element 28 than ablation elements 24. A temperature sensor 30is provided at distal end 10 and a proximal temperature sensor 32 isprovided proximal to ablation elements 24. Temperature sensors 30 and 32preferably comprise thermocouples. Temperature sensors 30 and 32 alsomay comprise thermistors and the like within the scope of the presentinvention. Temperature sensors or thermocouples 30 and 32 operate todetect the temperature in the region of ablation. A plurality ofinsulators 40 are provided between transducer elements 28 and ablationelements 24. Insulators 40 may comprise polyimide, polyesters, teflon orthe like to insulate transducer elements 28 from ablation elements 24.

Transducer elements 28 preferably comprise cylindrical transducerelements as best shown in FIGS. 4A-4B. Transducer elements 28 include anouter face 46 and an inner face 48. Inner faces 48 of transducerelements 28 are positioned such that a longitudinal axis 38 of body 12passes through a throughhole 44 of each transducer element 28. In such amanner, transducer elements 28 are configured to expose outer faces 46to surrounding tissue and fluid within the patient. In this manner,transducer elements 28 may operate to image within a 360° plane that isgenerally perpendicular to longitudinal axis 38 without the need torotate body 12 or transducers 28. It will be appreciated by thoseskilled in the art that other transducer shapes may be used within thescope of the present invention. For example, transducer elements 28 maycomprise rectangular or elliptical transducer elements operably attachedto distal end 10. Transducer elements 28 may comprise piezocompositematerials, piezoceramics (such as PZT), piezoplastics, and the like.

As best shown in FIG. 3, transducers 28 each may include a matchinglayer 42, or multiple matching layers 42, operably attached to the outerface 46 of each transducer element 28. Matching layers 42 operate toimprove transducer element 28 performance. In part due to the facttransducer elements 28 are used primarily as distance-to-tissuedetectors, transducer elements 28 also can operate without matchinglayers 42 within the scope of the present invention.

Transducer elements 28 have an outer diameter 29. Outer diameter 29 canbe less than an outer diameter 31 of flexible elongate body 12 or,alternatively, about equal to diameter 31. Preferably, diameter 31 ofbody 12 is less than about eight (8) French to permit the introductionof apparatus 2 into a patient's tortuous vasculature.

Gap 26 separates adjacent ablation elements 24. Gap 26 preferably isbetween about 1.5 mm and about 3.0 mm in width. Gap 26, however, can belarger or smaller in size and need not be of uniform size between eachtwo adjacent ablation elements 24. Similarly, each gap 26 need notcontain a transducer element 28, and gap 26 may contain more than onetransducer element 28 within the scope of the present invention.However, preferably at least some gaps 26 contain transducer elements28, and more preferably, each gap 26 between ablation elements 24contains one transducer element 28.

Elongate body 12 preferably includes a working lumen 39 through whichlongitudinal axis 38 passes. As best shown in FIG. 4A, matching layer 42extends around the outer surface of transducer element 28. Matchinglayer 42 is operably attached to transducer element 28, preferably usingepoxy or the like. Transducer element 28 can be operably attached toelongate body 12 in a variety of manners, including by epoxy. The use oflumen 39 is best shown in FIGS. 5A and 5B which depict two alternativeembodiments of tissue ablation apparatus 2 of the present invention.

FIG. 5A depicts the tissue ablation apparatus shown in FIG. 3 withoutmatching layers 42. As can be seen in FIG. 5A, a plurality of leads 50are operably attached to thermocouples 30 and 32, to transducer elements28 and to ablation elements 24. For an embodiment having electrodes forablation elements 24, each electrode has a single lead 50. Thermocouples30 and 32 each have a pair of leads 50. Transducer elements 28 have onelead 50 in electrical communication with outer face 46. Further, aground 52 extends from inner face 48 of transducer 28. As shown in FIG.5A, a common ground can be used for all transducer elements 28 within aparticular apparatus 2. The benefit of using a common ground 52 is thatfewer leads or wires 50 are passed from distal end 10, through lumen 39to controller 23.

The embodiment shown in FIG. 5B depicts the use of a multiplexer 54operably attached to distal end 10 of flexible elongate body 12.Multiplexer 54 preferably is operably attached proximal of ablationelements 24 and transducer elements 28. Multiplexer 54 permits theattachment of leads 50 from transducer elements 28 to multiplexer 54without the need to run those leads 50 to controller 23. Such aconfiguration can reduce the number of wires needed to be extendedthrough lumen 39 to controller 23.

The operation of multiplexer 54 is best described in conjunction withFIG. 6. FIG. 6 depicts transducer elements 28 each having ground 52 andlead 50. Leads 50 are operably attached to multiplexer 54, preferably onthe distal side of multiplexer 54. Multiplexer 54 has a ground 62 and atransmission line 60 for providing power to multiplexer circuit 54.Transmit and receive lines 56 provide a means to transmit electricalsignals to multiplexer 54. Multiplexer 54 then directs electricalsignals to the appropriate transducer 28. Transmit/receive wires 56carry transducer 28 excitation signals as differential pulses in seriesformat from controller 23 to multiplexer 54. At multiplexer 54, eachexcitation signal is routed to an appropriate one of the transducerelements 28 in order to execute an excitation sequence used bycontroller 23. Similarly, return echoes received by transducerelement(s) 28 are transferred to multiplexer 54 and return to controller23 along transmit/receive lines 56.

By minimizing the number of wires required to carry the excitationsignals from controller 23 to each of transducer elements 28, thediameter of elongate body 12, and more specifically, the size of lumen39 can be reduced. Alternatively, the number of transducer elements 28can be increased at distal end 10 without the need to require wires tobe run through lumen 39 to controller 23.

Multiplexer 54 further may include a clock line 58 extending fromcontroller 23 to multiplexer 54. Such a clock line 58 assistsmultiplexer 54 in determining which transducer element 28 is to receivean excitation signal. Alternatively, as shown in FIG. 6, clock line 58operates by counting the number of excitation signals transmittedthrough transmit/receive lines 56 and incrementing a counter inmultiplexer 54 to coordinate the transfer of excitation signals to theappropriate transducer 28. In one embodiment, multiplexer 54 alsoincludes a data line (not shown in FIG. 6) extending from controller 23to multiplexer 54. This data line permits controller 23 to control theoperation of multiplexer 54.

Turning now to FIGS. 7 and 8, the operation of tissue ablation apparatus2 and system 4 will be described. Tissue ablation apparatus 2 operatesby having transducer elements 28 detect the proximity of a tissue 70with respect to elongate body 12 distal end 10. Controller 23 calculatesthe time delay between transducer element 28 excitation and the receiptof a reflected signal 66 from surrounding tissue 70 to determine thedistance between transducer element 28 and tissue 70, as furtherdescribed below.

As shown by FIGS. 7A and 7B, an excitation signal 64 is transmitted fromcontroller 23 to transducer elements 28, or to multiplexer 54 fortransmission to transducer elements 28. Excitation signal 64 isconverted by transducer 28 into an ultrasound signal which propagatesout into surrounding fluid and tissues within the patient. Transducerelements 28 detect reflected signals 66 and transfer electricalrepresentations of those signals to controller 23 for processing.

Controller 23 uses the time delay between the excitation 64 and thereceipt of reflected signal 66 to calculate the approximate distance tothe reflecting object. Controller 23 is capable of differentiatingbetween low amplitude blood reflections and larger amplitude tissuereflections 66 as shown in FIG. 7. Controller 23 further differentiatesfrom a randomized back scatter versus more stable tissue scatter. Thedistance from each transducer 28 to tissue 70 may be calculated byknowing the speed of sound and measuring the time response to the largeramplitude tissue reflections. If the signal completely consists oflarger amplitude wave forms, intimate contact will be diagnosed. Whiletransducers 28 inherently have a blind zone/time period in which signalscannot be measured, the resulting blind zone is rather small. Forexample, for a 30 Mhz transducer, this distance is approximately 0.15mm. Hence, reflected signal 66 measured almost immediately afterexcitation 64 occurs results in the distance from the transducer 28 totissue 70 being less than about 0.15 mm blind distance.

Tissue ablation system 4, therefore, can be operated by inserting tissueablation apparatus 2 within the patient and positioning distal end 10 ofablation apparatus 2 near a desired location of the patient's anatomy.Transducer elements 28 are energized with excitation signal 64 andreflected signals 66 are received and processed by controller 23.Controller 23 determines whether or not transducer elements 28 are incontact with tissue 70. If at least one transducer element 28 is incontact with tissue 70, ablation using an adjacent ablation element 24may occur. Preferably, as shown in FIG. 8, it will be desirable to havemore than one transducer element 28 in contact with tissue 70.

Controller 23 can be operated in a variety of ways to determine thenumber and positioning of transducer elements 28 which may be in contactwith tissue 70. For example, as shown in FIG. 8, transducer elements28A, 28B and 28C would indicate that they were in contact with tissue70. This may permit the physician to ablate tissue 70 using electrode24A and electrode 24B. Transducer element 28D would not indicate contactwith tissue 70. Therefore, it is inconclusive whether ablation element24C is in contact with tissue 70. Hence, the physician may choose not toablate with ablation element 24C.

In one embodiment, controller 23 may use a green and red light systemfor indicating when transducer elements 28 are in contact with tissue70. In one particular embodiment, for example, controller 23 has a redlight and a green light for each transducer element 28A-28D depicted inFIG. 8. The green light would be illuminated by controller 23 when thecorresponding transducer element 28 is in contact with tissue 70. Redlights would be illuminated for those transducer elements 28 not intissue contact.

Alternatively, a single green and red light may be used for apparatus 2,whereby the green light is illuminated by controller 23 only when alltransducer elements 28 are in tissue contact. Still another embodimentinvolves several transducer elements 28 corresponding to a singlegreen/red light set. For example, elements 28A and 28B may have onegreen light which controller 23 illuminates when both elements 28A and28B are in tissue contact. The red light corresponding to elements 28Aand 28B would be illuminated if one or both transducer elements 28A and28B are not in contact with tissue 70. It will be appreciated by thoseskilled in the art that there exist numerous ways within the scope ofthe present invention for controller 23 to indicate when tissue 70contact has been achieved by transducer elements 28, including audibletones and the like.

Ablation elements 24 are preferably used for mono-polar ablation,although bi-polar ablation also is anticipated within the scope of thepresent invention. Ablation elements 24 preferably comprise electrodes.In this manner, RF ablation may occur using ablation elements 24.

Alternatively, ablation elements 24 may comprise ablation ultrasoundtransducers. In this manner, transducer elements 28 are operated inpulse mode to determine their distance from tissue 70. Upon tissuecontact, ablation transducers 24 would be used to ablate tissue 70. Theuse of transducers for acoustic ablation is further described in U.S.Pat. No. 5,630,837, the complete disclosure of which has been previouslyincorporated by reference.

Alternatively, transducer elements 28 can be used to both image andablate tissue 70. Transducer elements 28 would first be operated inpulse mode, to determine whether transducer elements 28 are in contactwith tissue 70. Transducer elements 28 then would receive a continuouswave or gated continuous wave electrical signal having a frequency ofabout 10-15 MHz, and transducer elements 28 would ablate tissue 70 usingultrasound ablation.

The invention has now been described in detail. However, it will beappreciated that certain changes and modifications may be made. Forexample, while FIGS. 2, 3, 5 and 8 depict transducer elements 28interspaced between all ablation elements 24, transducers 28 may onlyexist between some of ablation elements 24 and in same gaps 26.Therefore, the scope and content of this invention are not limited bythe foregoing description. Rather, the scope and content are to bedefined by the following claims.

What is claimed is:
 1. A system for ablating tissue, comprising: anablation apparatus comprising, a flexible elongate body having a distalend and a proximal end; a plurality of spaced apart ablation elementsoperably attached to said flexible body near said distal end; aplurality of transducer elements disposed between at least some of saidablation elements; and a temperature sensor coupled to the distal endand positioned distal to the plurality of ablation elements and distalto the plurality of transducer elements; and a controller in electricalcommunication with said ablation elements and said transducer elements;wherein each said ablation element has at least one said transducerelement adjacent thereto, and wherein each said ablation element has atleast one of said transducer elements located distal thereto.
 2. Asystem as in claim 1, wherein said transducer elements and said ablationelements are operably attached to said flexible body in an alternatingfashion.
 3. A system as in claim 1, wherein said plurality of ablationelements comprise a plurality of electrodes.
 4. A system as in claim 1,wherein said plurality of ablation elements comprise a plurality ofablation transducer elements.
 5. A system as in claim 1, wherein saidcontroller comprises an ultrasound imaging and ablation controller.
 6. Asystem as in claim 1, further comprising a plurality of leads, whereinat least one lead is operably attached to each of said ablation elementsand each of said transducer elements.
 7. A system as in claim 6, whereinsaid plurality of leads are in electrical communication with saidcontroller to allow a plurality of electrical signals to be sent by saidcontroller to said ablation elements and to said transducer elements. 8.A system as in claim 6, further comprising a multiplexer operablyattached to said flexible body and in electrical communication with saidcontroller, and wherein at least some of said leads are operablyattached to said multiplexer.
 9. A system as in claim 1, wherein saidtransducer elements comprise cylindrical transducer elements.
 10. Thesystem as in claim 1, wherein each of said ablation elements has atleast one of said transducer elements located proximal said ablationelement, and at least one of said transducer elements located distalsaid ablation element.
 11. The system as in claim 1 wherein saidtransducer elements comprise cylindrical transducer elements, saidelements each having a throughhole, and wherein said transducer elementsare positioned so that a longitudinal axis of said flexible body passesthrough said throughholes.
 12. The system as in claim 1 furthercomprising a plurality of insulators operably attached to the elongatebody and positioned so that each of the ablation elements has at leastone insulator positioned between the ablation element and the adjacenttransducer element.
 13. The system as in claim 1 wherein the transducerelement adjacent said ablation element is directly distal to theablation element.
 14. The system as in claim 1 wherein the transducerelement adjacent said ablation element is directly proximal to theablation element.
 15. The system as in claim 1 wherein each of saidablation elements has at least one transducer element located proximalthereto.
 16. A method of ablating tissue comprising: providing a tissueablation apparatus, said apparatus comprising a flexible elongate body,a plurality of ablation elements and a plurality of transducer elements,said ablation elements and said transducer elements being operablyattached to said body so that each of said plurality of ablationelements has at least one of the plurality of transducer elementslocated distal thereto and at least one of the plurality of transducerelements located proximal thereto, the plurality of ablation elementsand transducer elements coupled to a controller; inserting said ablationapparatus into a patient; positioning said ablation apparatus withinsaid patient so that said ablation apparatus is proximate a tissue to beablated; energizing said transducer elements; receiving a plurality ofreflected signals from said transducer elements; processing saidreflected signals to determine if said transducer elements are incontact with said tissue to be ablated; and activating at least one ofsaid ablation elements to ablate said tissue if said controllerdetermines that at least one of said transducer elements adjacent saidat least one ablation element is in contact with said tissue.
 17. Amethod of ablating tissue as in claim 16, wherein said plurality ofablation elements comprise a plurality of electrodes for supplyingcurrent to said tissue.
 18. A method of ablating tissue as in claim 16,wherein said plurality of ablation elements comprise a plurality ofablation transducers, and said activating step comprises activating saidablation transducers to ablate said tissue using ultrasound energy. 19.A method as in claim 16, further comprising activating said transducerelements to ablate said tissue using ultrasound energy.
 20. The methodof claim 16 wherein the number of transducer elements exceeds the numberof ablation elements by at least one.
 21. The method of claim 16 whereinsaid apparatus comprises between about two and about fourteen ablationelements, and between about three and about fifteen transducer elements.22. The method as in claim 16, further comprising activating the atleast one ablation element if the controller determines one of saidtransducer elements located directly adjacent the ablation element is incontact with the tissue.
 23. The method as in claim 16 furthercomprising activating the at least one ablation element if thecontroller determines that one of the transducer element s locateddistal to the ablation element is in contact with the tissue, and thatone of the transducer elements located proximal to the ablation elementis in contact with the tissue.
 24. The method as in claim 23 furthercomprising activating the at least one ablation element if thecontroller determines that the transducer element immediately distal theat least one ablation element and the transducer element immediatelyproximal the at least one ablation element are both in contact with thetissue.